264This section focuses on biomarkers used in the diagnosis and prediction of preterm labor (PE). Preterm labor is a complex condition and although it has different etiologies, it ultimately results in preterm labor caused by uterine contractility, cervical changes and rupture of membranes. Accurate diagnosis and foresight in preterm labor ensures the implementation of appropriate interventions. This text provides information about biomarkers in cervical fluid, amniotic fluid or maternal serum used to predict PE. It highlights the use of certain biomarkers such as fetal fibronectin (fFN). fFN is a protein found in cervicovaginal fluid, and its presence in the cervicovaginal fluid of women at risk of preterm labor may increase the risk of preterm delivery. However, fFN results alone are not useful and other biomarkers need to be investigated. This text also draws attention to the necessity of investigating and combining different biomarkers in the prediction of PE.

It is thought that amniocentesis performed in the second trimester may provide important biomarkers for PE risk. Low amniotic fluid glucose and high IL-6 levels are associated with the risk of preterm birth, while maternal serum ferritin levels increase, while serum albumin levels decrease. Also, elevated IL-1β levels in amniotic fluid and cervicovaginal fluid have been suggested as a predictor for PE. While VEGF and PGF levels in amniotic fluid increase, sFlt-1 levels decrease. Neutrophil elastase levels can be used to predict the risk of PE after emergency cerclage. Finally, a combination of IL-8 and annexin-A2 levels in amniotic fluid can be used to predict the development of PE with or without preterm premature rupture of membranes.

Studies on some maternal serum biomarkers that can be used to determine the risk of preterm birth are still ongoing, and the biomarkers that have been found to be related are as follows:
Maternal serum calponin1 was found to be high in women who will have preterm delivery.
The maternal serum alpha fetoprotein (AFP) / amniotic fluid AFP ratio may be a marker for intrauterine growth retardation and PE.
Progesterone induced blocking factor (PIBF) in maternal serum was found to be significantly lower in the pre-PE period.
The maternal platelet count was found to be high in women with preterm delivery.
Maternal salivary estriol measured at 25-34 weeks can be used to identify women who will not deliver preterm.

In addition, it is emphasized that early interventions can reduce the risk of PE, it is important to identify risk factors in early pregnancy and PE is a complex condition caused by multiple etiological pathways. It is stated that the variability in the results of the studies may be due to the different study designs and the variation in the study population and it is necessary to study on a large sample to confirm the efficacy of a biomarker.